Companion, you are a turd.

I wouldn't' be so sure about that. For all of the might ad power that magic is (and there is no doubt magic is powerful), that hasn't stopped it from being trounced by politics. Politics is what keeps the mages in Circles, politics is what keeps mages out of power in the south, politics is what constantly tries to keep a firm hand on magic.

Outside of Tevinter at least, politics is more 'powerful' than magic. They have nations, treaties, numbers and in the Chantry's case, magic countermeasures (Templars). Meanwhile magic has solidarity within the highly regulated Circle and hedge mages that dare not show their faces in society lest they be tracked by Templars or killed by townspeople.

As for Morrigan though....I honestly thought it was because of either the eluvians or simply having more mage-mystique than Vivienne. Morrigan simply seems more mystical and interesting than most Circle mages precisely because it is so unorthodox. It's unusual, its exotic, it's exciting. We already know that word around the court is that the Empress is highly interested  in the occult and mysticism--something which Morrigan practically specializes in as the daughter of Flemeth obsessed with old knowledge and secrets.

Even if Morrigan was simply bland and had no power to speak of, she does still have something that would likely interest the Empress--knowledge of the eluvians. After the fallout in Masked Empire, Celene is probably still interested in the advantage the eluvians could give, but she knows she could no longer rely on Briala to give them to her.